Violent and massive events in our universe create brilliant gamma-ray displays that will keep the Fermi Gamma-ray Space Telescope busy for a decade. But recently, Fermi has turned its eyes back to Earth, where it can see evidence of Terrestrial Gamma Flashes, or TGFs, which are believed to originate at the tops of thunderstorm clouds. Fermi announced that it has detected positrons from TGFs, a first result and a major clue about what actually causes them.